The PHB description of Bonus Action is pretty interesting if you look at how they are treated in BG3:
B o n u s A c t io n s
Various class features, spells, and other abilities let you
take an additional action on your turn called a bonus
action. The Cunning Action feature, for example, allows
a rogue to take a bonus action. You can take a bonus
action only when a special ability, spell, or other feature
o f the game states that you can do something as a bonus
action. You otherwise don’t have a bonus action to take.
You can take only one bonus action on your turn, so
you must choose which bonus action to use w hen you
have more than one available.
You choose when to take a bonus action during your
turn, unless the bonus action’s timing is specified, and
anything that deprives you o f your ability to take actions
also prevents you from taking a bonus action.
So the way BAs are used in BG3 is already a full "homebrew" choice. That underlines that Larian just did it for laughs. My guess is that, after they designed shove, they found it so funny they decided that has to happen on a regular basis...meaning each round as much as possible. Ruining combat balance for this...
Just a guess though.
Even using a potion should be considered an action.
